Tread linkage



July 26, 1932.

A. ARMINGTON TREAD LINKAGE 2 Sheets-Sheet 1- Filed I Jan. 8, 1931 INVENTOR.

I ATTORNEY? July 26, 1932. A; P. ARMINGTON TREAD LINKAGE Filed Jan. 8, 1951 2 Sheets-Sheet 2 L10 /0 INVENTOR 49777 1? FARM/Nam ATTORNEYS Patented July 26, 1932 UNITED smrss PATENT oFFicE ARTHUR I. emmer-on, or WILLOFUGHBY, oHIo, ASSIGNDR To 'TH'E EUCLID elm-NE & H0181 GOMPANY, or EUcL-In, OHIO, a oonronn'rrorq or oHIo Applicat on fi ed was s, 1931- serial no. ent r This invention relates to endless tread linkages of the -.s0-ca. l d t s-fo y adapted for employment in vehicles as wheel substitutes- Such a linkage is usually 'n trained about long tu al yv p d p ir f wheels a one side of the vehicle, so that the fo mat t linkage w ll i c ud ig about the wheels and stretches tl erebetween, with the lower stretch resting upon the ground. Where the linkag i o trussi g yp its nature'is such that the ground-engaging stretch will serve asa beam in supporting the whe els, tha t is, will be incapable of fiexure upwardly between the wheels.

A linkage cap able of so functioning s not new an will be fou d -.il tra d and escribed in the Patent No. 1,623,457,issue ;l Ap il 1. .27 t0 1- ether, an n m e l er paten s, i ns h c i w l be e that the stretches may be straight, or sl ghtly u ved, dep n i g spoi the desig the truss-farmi g pa t v i The typical 'linl for such a linkage coin prises as its prinoi-palparts (l) ,a shoe having ground-engaging surface, with hinge-pinreceivinglugsuat its endswhere'by the linkage em ly i had, nd (2) russ-form la means pstanding rom the shoe pposi e th ground-engaging surface of the latter. U ual y the' e extend l ter lly (i either side-bey nd the tru -formi g pa of the link, which latter are vcent a ly located, the shoe extensions providing rails 'for bear ng he wh ls The wheels are hus empl y in coax a p r ,,.one on ei h id o h truss-forming parts of the linkage, which lat e ext ncl etwee the Whe l At any rate, in the ground-engag ng stretch of the linkagethe beam characteristic fis d y interengagem h f h trus -fenni -g pa ts of t several 1i k .,,ahove the e tri l xi andthu a ting in tension with respectto the stretch; and by the. shoe portions of the links, belowthe neutral axis, acting'in cemi e on- Si ce h eo me tion'be een the i k oe portions is t ugh the hi ge pi s, t n i e loa i transmitted d e tly through those hinge pins in the stretch. N it is des ra le th t ee ings, unfinish at l a t o their trus -forming part be employed for the links; so that, however good the foundry work, and'however close the original fit of the linkage about its wheels, some early wear or running in of the assembly will rapidly take place, after which-the wear of thetruss-forn ing parts will be relatively slight fora relatiyely long period of time, This is one of the reasons for providing initial outward curvature in the link age stretch; that the stretch shall not curve inwardly after .wear.

In addition, in any such linkage there must i be some initial slack to provide working Clearances for free running'of the parts.

lVitjh reference to the pins, however, and those parts in which they bear, continuous Wear will result thereupon so long as relative motion of an adjacent pair of links takes place while the pins are loaded bybending stresses in the beam-forming stretch of the linkage; so that the total slack in the linkage will rapidly increase if limiting means are notlprovided, Much slack is very undesirable, as it develops friction, and ultimately allows theground-engaging stretch to sag upwardly and thus greatlyincreases draft regliren entsj enerally the objects of this invention are to provide an arrangement whereby there may be less initial slack in the linkagea'nd whereby reduced wear atthehinge pins will follow; 7

Mor specifically i i e o i ec of the pr ent inven ion .to adv n aged he above described and unavoidable wear in the linkage, or rather of the relatively slight slack resulting,therefronn to provide that the hinge pins shall vnot be loaded during motion of the corresponding inks thereabout. Briefly I acconiplisli this by pro-len ing the hearing of the forward Wheel ,upon the forward end of the firstlink in the ground engaging stretch, until the next forward link moves from the bend. onto the stretch of the linkage as the wheel rolls ahead. To thisiend I ex? tend the rail portion of the link beyond the center of, and indeed entirely beyond, the forward hinge-pin-receiving opening ,of the link. i

a The egractnature of this invention together 7 members.

with further objects and advantages thereof will be apparent from the following description taken in connection with the accomforwardly, the links appearing being shown in their entirety, Fig. 5, except that some are cut away to show details of construction, but the shoe portions only of the same links appearing Figs. 68.

With reference now to the drawings the link chosen for illustration, Figs. 1-4, includes a shoe portion 1 having a ground-engaging or tread surface 2. Upstanding from the shoe centrally thereof are truss-forming These members are here shown as including a hook member 3 and an eye memher 4:, the hook member having a surface 5 adapted to engage a. corresponding inside surface 6 of the eye member of another simi lar link. These truss-forming members are preferably integral with the shoe, and include the reinforcing webbing and flanges indicated in the drawings whereby a typical section through the hook member is of I 7 characteristic, and that through the hook member is of box form.

trated a pair of lugs 8 extend rearwardly and have aligned openings 9; and at. the front end of the shoe three lugs 10, 11, and 12, laterally offset from the rear lugs, extend forwardly and have aligned openings 13. The dimensions and spacing of the rear lugs 8 are such that each will fit between two of the front lugs of a similar link, so that a hinge pin may be passed through the two openings 9 of the rear lugs of one link and the three openings 13 of the forward lugs of the other link, with the hook member 3 of the forward link extending within the eye member 4 of J the rearward link.

It is to be noted that the outer pair of the forward lugs extend forwardly of the wheelcarrying side or rail portions 7 of the link shoe and are thus adapted for wheel-carrying. With this principal exception such genforming parts; and it will suffice here to say that a linkage of such links may bend freely at the hinge pin joints inwardly as shown at the right Fig. 5, but may not bend from straightened position in the opposite direction. The bending in the one direction is allowed by movement of each hook member 3 within the eye member 4 of the next adjacent link as shown at the right, Fig. 5; but bending in the opposite direction is prevented by interengagement of the hook face 5 of one link with the eye face 6 of the next link as shown at the left Fig. 5.

More accurately, in the ground-engaging stretch of the linkage cooperative faces 5 and 6 of the truss-forming parts are above the neutral axis of the linkage so that these parts act as the chord or tension part of the beam; and the hinge pins 17 by which the linkage assembly is had, together with the shoe portions of the links, are below the neutral axis so that these parts must act as struts, generally stressed in compression in the beam. Of course, whereas the link shoes are actually stressed in compression in the beam-forming stretch of the linkage, the hinge pins are stressed as a result principally in shear. At any rate it will be obvious that. the maximum load upon the hinge pins and their bearings will be when the latter are in ground-engaging stretches of the linkage with the trussforming parts of the links interengaged to provide the beam characteristics; and indeed stresses upon these parts are negligible in other positions in the linkage. ing'the wheel indicated by a broken line 14 Fig. 5, to be the leading wheel of a pair rolling upon the near shoe side portions 7 of the linkage, the linkage may be bent about the Thus assuml pair of wheels, but the stretches between the wheels will beinflexible inwards thereof, that is, the stretches will be rigid, acting as beams, against forces tending to move them toward each other. This is unimportant as to the upper stretch but of course it is important as to the lower or ground-engaging stretch, as will be appreciated by one familiar with the art.

Returning now to Figs. 13, the shoe portion of the link at each side of and adjacent the truss-forming portions may be slightly raised as at 15 to provide a rail surface. As shown, Figs. 1 and 3, this rail surface extends forwardly over and along the corresponding forward hinge-pin-receiving lug 10, 12. The rail extends on its hinge-pin-receiving lug forwardly beyond the hinge-pin-receiving opening 13 thereof and up to a point where it will just clear the shoe portion of the next adjacent link of the linkage when at the bight of the linkage. Thus a shoulder 16 is had on each wheel-carrying lug at its forward end.

Inspection of Figs. 1 and 3 will show that the length of the rail surface 15, the effective memos length of the rail, closely approaches the spacing between the centers of the hinge pin openings 9 and 13 of the link, but that the rail is offset ahead of the center of the link; that is, the rail extends forwardly beyond the main body part of the link, and the rail terminates rearwardly ahead of said body part.

With reference now to Figs. 5-8 and first to Fig. 5, a pertinent portion of a linkage of such links appears, and the linelt indicates the treads of a pair of coaxial parallel Wheels one bearing upon each of the two tracks provided by the rails 15 of the linkage so that the truss-forming parts extend radially inwards between the two wheels. In Figs. 5-8, the wheels indicated at 14 are assumed to be leading wheels, rolling forwardly, to the right in the drawings as indicated by the straight arrows; all generally as appears in Fig. 1 of the patent to Athey, identified above, except that in Figs. 58 herein as sumed movement is to the right whereas in Fig. 1 of the Athey patent assumed movement is to the left and for convenience the ground-engaging stretch is shown as straight.

As before described, in such a linkage so arranged, a certain slack is bound to develop and this slack will be largely confined in operation to the lower portion of the bend or bight of the linkage about the forward wheel or wheels; and such slack is shown in Figs. 58.

In Fig. 5, as indicated by the vertical line 18 extending radially of the wheel, the tangency or bearing of the wheel upon its track is about central of the rail portion 15 of the link 19; those links immediately behind the link 19, beginning with the link 20, function in the ground-engaging stretch of the linkage, as described, imparting beam characteristics thereto; and those links immediately ahead of the link 19 commencing with the link 21, being in the bend of the linkage are substantially unstressed. Thus the rearward hinge pin of the link 19 is heavily loaded but there is no movement thereabout; while there may be movement about the forward hinge in of the link 19 but this pin is not loaded Such conditions maintain while the progression of the parts is had to the position indicated in Fig. 6, the link 21, still unloaded, swinging downwardly in approach to ground-engaging position, that is, to a posi-. tion in which its shoe surface 2 bears against the ground; or more accurately, to a position in which its truss-forming parts engage those of the next link 19, ahead in the cycle.

In Fig. 7 the center of the wheel and thus the load has passed beyond the center of the forward hinge pin of the link 19. The load is still, however, entirely upon the link 19 being carried by the shoulders 16 of this link. The next forward link 21 is still unloaded although it is now in load-carrying position, Comparison of Figs. 6 and 7 will show thatthe slack of the linkage is just nicely suflicient to allow the swing of the link 21 between these two positions, the forward end of the next forward link 22 swing ing somewhat upwardly as the forward end of the link 21 swings downwardly,

In Fig, .8 the wheel has progressed from the shoulder 16 of the link 19 onto the rail portion 15 of the link 21. The hinge pin joining the links 19, 21., 110W Carries its load but there is no motion thereabout between the links 19 and 21. The shoulders 16 being considered as an extension of the rail 15, the gap in the wheel track between the successive rail sections on the several links is much reduced; so that an approximately continuous rail is provided for the wheel. It is particularly to be noted, however, that the interruptions between rail sections are ahead of the hinge joints between corresponding links.

The described cycle is now repeated by the link 21 as the wheel rolls thereover, and thereafter by all of the links in succession.

What I claim is:

1. A tread link adapted for hinge connection with similar links in a linkage to provide a track-forming ground -engaging stretch having beam characteristics for supporting a pair of vehicle wheels, said link comprising, when disposed as in said stretch, a shoe having a tread surface, and on its opposite ends hinge lugs, the lugs on one end eing offset laterally from those on the other end, said shoe having a wheel supporting rail overlying a forward one of said lugs, said lug having a shoulder bearing a continuation of said rail extending forwardly beyond its hinge axis to provide a total length of said rail closely approaching the spacing between the hinge axes of the link, the center of said rail being ahead of the center of said shoe, and truss-forming parts extending upwardly of said shoe beyond said rail and adapted to cooperate with corresponding parts of the next adjacent links of the linkage.

2. A tread linkage adapted toprovide a track-forming ground-engaging stretch having beam characteristics for supporting a pair of vehicle wheels, and to extend in said stretch from a bend about the leading wheel, each link of said linkage comprising a shoe having a tread surface and end lugs, hinge pins in said lugs to connect the links, each shoe having a rail and one of said lugs extending forwardly thereof and bearing a forward extension thereof beyond the. corresponding pin, whereby said linkage provides in effect a continuous rail for said wheels, in rail sections disposed end to end, with interruptions between said rail sections ahead of the joints between corresponding links, said linkage including truss-forming cal parts extending upwardly from said shoes beyond said rail and adapted to prevent upward bending of said stretch between wheels running thereon, the arrangement being such that a link will not assume the load of said leading Wheel until its said truss-forming parts thereof are engaged by those of the adjacent link from which the Wheel runs.

In testimony whereof I hereby aifix my signature.

ARTHUR P. ARMINGT'ON. 

